Ch. 7 Skull Bones Flashcards
Cranial Cavities
- largest cavity which encloses, cushions and supports brain
- smaller cavities: orbits, oral cavity, nasal cavity, paranasal sinuses
Paranasal Sinuses
- frontal, sphenoid, ethmoid, and maxillary bones
- lined with some mucous membranes that line nasal cavity
- sinuses lighten the skull’s mass and increase surface area; moisten and cleanse inhaled air
- resonating chambers that intensify and prolong sounds; enhancing quality of person’s voice
Sutures
- immovable joint in adults
- coronal: unites frontal and parietal bones
- sagittal: unites the two parietal bone
- lambdoid: unites two parietal bones to the occipital bone
- squamous: unite the parietal and temporal bones
Fontanels
- unossified mesenchyme that will be replaced with bone by intermembranous ossification
- provide flexibility to the fetal skull, allows skull to change shape through birth canal and permit brain growth
Frontal Bone- SIngle
- forms anterior roof of cranium, nasal cavity and arches of orbits
frontal squama: platelike bone, forms the forehead
supraorbital margin: prominent bony ridge
supraorbital foramen: opening in margin where supraorbital nerve passes
frontal sinuses: reduce the weight of skull
Parietal bones- paired
- large and quadrilateral
- form much of the sides and roof of the cranial cavity
- articulate with 5 other bones
- seperated by coronal, squamous and lambdoid sutures
Temporal bones- paired
- form the inferio-lateral part of the cranial floor plus part of the lateral wall near the ear
- extend a narrow process forward towards the zygomatic bone forming the zygomatic arch
- articulate with the mandible at the TMJ
- mastoid process is a prominent surface feature just behind the below the ear
Mastoid Portion
- rounded projection of the mastoid portion of the temporal bone is prosterior and inferior to the ext. auditory meatus
- serves the attachment fir the several neck muscles
- internal auditory meatus serve the opening for the facial (VII) and vestibulocochlear (VII) cranial nerves
- styloid process serve the attachment for mucles and ligaments of the tognue and neck
- stylomastoid foramen serves the passage for facial (VII) and stylomastoid artery
Petrous portion
- houses sensory organs for hearing and equilibrium
- located at the base of the skull between the sphenoid and occipital bones
- middle ear consists of three ear ossicles
- houses the carotid foramen for carotid artery
- houses jugular foramen for the jugular vein; formed by adjacent notches in the temporal and occipital bones
Occipital Bone- single
- forms much of posterior wall and the posterior floor of the cranial cavity
prominent surface features: foramen magnum, occipital condyles, external occipital protuberance, ligamentum nuchae
Sphenoid Bone- single
surface features of sphenoid bone: forms the middle part of the base of the skull, resembles butterfly shape
consists of: body, sphenoid sinus, sella turica, tuberculum sellae, hypophyseal fossa, dorsum sellae
Sphenhoid Bone Consists of…
superior orbital fissure: opthalamic trigeminal, ocular, trochlear and abducens nerves
foramen rotundum: maxillary nerve
foramen ovale: for mandibular nerve
foramen spinosum: for internal cartoid and pharyngeal artery
Skull Markings
superior orbital fissure: for opthalmic trigeminal, ocular, trochlear and abducens nerves
foramen rotundum: for maxillary nerve
foramen ovale: for mandibular nerve
foramen spinosum: for internal cartoid and pharyngeal
optic foramen: optic nerve and opthalmic artery
Ethmoid Bone- single
- numerous paranasal sinuses
- form anterior part of the cranial floor (the cribriform plate) through which numerous foramina pass
- medial wall of the eye sockets
- superior portion of the nasal septum
- much of the nasal cavity walls
- houses ethmodial cells which becomes ethmoid sinuses
- olfactory formina- passes olfactory nerve (I)
Facial Bones (14)
- facial bones are not in contact with the brain
- along with cranial bones, these bones provide shape and individual face features
- support teeth and provide attachments for various face and jaw muscles
- except the bones of the yomer and mandibles, all facial bones are paired
Nasal- paired
- contains rectangular bone that forms the bridge of the nose
- supports the flexible cartilaginous plates, forms framework of the nose
supports thin muscles of facial expression - common site for facial injuries
Lacrimal- paired
- smallest bone of the face
- these are paired bones that form the anterior portion of the medial wall of the eye socket
- a bony depression that continues into the maxilla, called the lacrimal groove, accepts a soft tissue tube (lacrimal sac) that passes tears from the eye into the nasal cavity
Palatine- Paired
- paired L-shaped bones that form the posterior edge of the hard palate as well as portions of the eye socket and nasal cavity wall and floor
Inferior Nasal Conchae- paired
- inferior nasal conchae are seperate bones, distinct from the superior and middle conchae which are projections from the ethmoid
- all conchae help to swirl and filter air before it passes into the lungs
- only the superior nasal conchea of the ethmoid bone increase the surface area and aid in sense of smell
Vomer- single
- unpaired bone, the vomer sits on the floor of the nasal cavity
- extends a bony partition superiorly that meet the perpendicular plate of the ethmoid; together they form the nasal septum
- divides the nasal cavity into right and left
Maxillae- paired
- paired maxillary ones fuse at the midline to form the upper jaw
- internally, maxillae contribute to the inferior wall of orbit, the walls and floor of the nasal cavity, and most of the hard palate
- body of the maxillae are hollowed out internally to form a pair of large sinuses
- contains body, alveolar process and infraorbital foramen
- this foramen passes infraorbital blood vessels and nerves
zygomatic (cheekbone)- paired
- these bones form the prominences on the anterior face called cheekbones
- temporal process of zygomatic bone projects posteriorly and articulates with the zygomatic process of the temporal bone to form zygomatic arch
- zygomatic foramen passes zygomaticofical nerve and blood vessels
Mandible- single
- arched bone is the largest and strongest bone that forms that lower jawbone
- only moveable bone of the facial bones
structural features include: body, rami, angle, condylar process (mandibular fossa of temporal bone (TMJ)), coronoid process (temporalis muscle), mandibular notch, mental foramen
Orbit of the Eye
formed by cranial and facial bones: frontal, zygomatic, sphenoid, ethmoid, lacrimal, maxilla
- 3 cranial bones, 4 facial bones
- associated with each orbit are 5 openings: optic foramen, superior orbital fissure, inferior orbital fissure, supraorbital foramen, lacrimal fossa
Cranial Fossae
- cranium has 3 distinct regions called cranial fossae that correspond to the major contours of the inferior surface of the brain
- from anterior to posterior they are:
- anterior cranial fossa, middle cranial fossa, posterior cranial fossa
Anterior Cranial Fossa
- formed by the portions of the frontal bone that constitutes the roof of the orbits and nasal cavity, the crista galli and cribiform plate of the ethmoid bone, and the lesser wings and part of the body of the sphenoid bones
- this fossa surrounds the frontal lobes of the cerebral hemispheres of the brain
Middle Cranial Fossa
- located inferior and posterior to the anterior cranial fossa, the middle cranial fossa is shaped like a butterfly
- median portion is formed by part of the body of the sphenoid bone, and the lateral portions are formed by the greater wings of the sphenoid bone, temporal squama, and parietal bone
- this fossa cradles the temporal lobes of the cerebral hemispheres
Posterior Cranial Fossa
- largest of the fossae
- formed mostly by the occipital bone and the petrous and mastoid portions of the temporal bone
- very deep fossa that accommodates the cerebellum, pons, and medullar of the brain
Hyoid Bone
- unpaired and does not articulate with any other bone
- suspended from styloid processes of the temporal bones by ligaments and muscles, serving as a attachment site for muscles of the tongue, nack and pharynx
- hyoid bone consists of horizontal, rectangular body, and paired projections called the lesser horns and greater horns
Muscles of Facial Expression (17)
- muscles are located in a superficial postion on the scalp, face, and neck
- originate on the bones of the skull and insert into the skin
- innervated by the facial nerves
- location and point of attachment cause movements around eyes, nostril or mouth
Scalp- Occipitofrontalis
- refracts (draw) the scalp anteriorly, eyebrows, wrinkle skin of the forehead
- frontal bone
- epicranial aponeurosis
nose (2)- Nasalis
- compresses bridge and depresses tip of nose, elevate corner of nostrils
- maxillae and alar cartilage of nose
- dorsum of nose
Nose- Procerus
- moves nose, changes position and shape of nostril
- nasal bone and lateral nasal cartilage
- aponeurosis of a bridge of nose and skin of forhead
Buccinator
- compresses cheeks and lips, hold food between teeth during chewing
Orbicularis Oris
- kissing muscle; compresses and purses lips
Depressor Labil Inferioris
- draws lower lip inferiorly
Depressor Anguli Oris
- draws corner of mouth inferiorly and laterally
Levator Labil Superioris
- opens lips, raises and furrows the upper lip
Levator Anguli Oris
- draws corners of mouth superiorly and laterally
Zygomatics Major and Minor
- elevate the corner of the mouth superiorly and laterally; smile muscles
Risorius
- draws corner of the mouth laterally, tenses lips, synergistic of zygomaticus (laughter)
Mentalis
- wrinkle chin, protrude lower lip
Neck (2)- Platysma
- pulls lower lip inferiorly and poseriroly, tenses skin of the neck
Orbicularis Oculi
- closes eye
Corrugator Supercili (eyebrow muscle)
- draws eyebrow inferiorly and wrinkles skin of forehead vertically as in frowning
Extrinsic Eye Muscles
- 6 extrinsic eye muscles control movements of each eyeball; originate on the outside of the eyeballs in the bony orbit and insert on the outer surface of the sclera
- those muscles with the word “rectus” in their name have obvious actions
- actions of the two oblique muscles cannot be deduced from their names
- often called extraocular muscles
- move the eyes
Rectus Muscles
- medial: moove eyeball medially (adducts)
lateral: moves eyeball laterally (abducts)
inferior: moves eyeball inferiorly (depresses) and medially (adducts) and rotate
superior: moves eyeball superiorly (elevate) and medially (adducts) and rotate medially
Oblique Muscles
- inferior: moves eyeball superiorly (elevate) and laterally (abduct) and rotate laterally
superior: moves eyeball inferiorly (depress) and laterally (abduct)
Muscles of Masticatoin
Large Temporalis: elevate and retract mandible
Medial and Lateral pterygoid: provides grinding movement of teeth (elevate), protracts mandible and strengthens the bite
3. Messeter: elevate and protract the mandible, prime mover of the jaw closure
Muscles that move Tongue and Help Chewing
- tongue important for mastication, taste, swallowing and speech
- divided into lateral halves by a median fibrous septum; inferiorly, septum attaches to the hyoid bone
- 2 types: extrinsic: originate outside the tongue and insert into it, moving entire tongue in various directions
intrinsic: originate and insert within the tongue, altering the tongue’s shape
Muscles that move the tongue
genioglossus (intrinsic): depresses and protracts (stick out) tongue
styloglossus (extrinsic): elevates and retracts tongue
Muscles of Pharynx that assist in swallowing and speech
pharyngeal constrictors:
- superior
- middle
- inferior
- these muscles constrict pharynx in sequence to force bolus into esophagus
Muscles of the anterior neck that help swallowing and speech
suprahyoid muscles: superior to the hyoid
infrahyoid muscles: are inferior to the hyoid
- both groups of muscles stabilize the hyoid bone, allowing it to serve as a firm base on which the tongue can move
Suprahyoid Muscle Group
Didastric: depresses mandible, elevate hyoid bone
Mylohyoid: elevates hyoid bone and elevate floor of the mouth
Infrahyoid Muscle Group
Sternohyoid: depresses hyoid bone
Thyrohyoid: depresses hyoid bone and elevates thyroid cartilage of larynx
